Classé Sigma 2200i integrated amplifier

The last few years have seen a flood of new integrated amplifiers in an audiophile market traditionally wedded to separate preamps and power amps. That might reflect the fact that integrated amps make a lot of sense, and not only because they usually cost less than equivalent separates. The latter gained a foothold in audio's Paleolithic era, when tubes were the only game in town. Tubes generate lots of heatan enemy of electronicsand separating the preamp stages from the output devices kept this under control. Yes, there were integrated amplifiers back then, but they were generally of very low power25Wpc was once considered monumental.

But when cooler-running solid-state components became practical, they followed the same path, probably more because of tradition than necessity. Audiophiles expected separates, and considered integrated amps to be, at best, mid-fi receivers with delusions of grandeur.

The result is that today's market is awash with discrete electronic boxes of every variety: DACs, phono preamps, line-level preamps, power amps, headphone amps, even room equalizers. Some of these devices themselves comprise separate enclosures for their housekeeping circuitry and power supplies.

So while not everyone agrees that incorporating all of a system's electronics into a single case is a good idea, it's hard to deny its practicality. There are, of course, different levels of consolidation. Some integrated amps include just a line-level preamp and stereo power amp; others do virtually everything. While adding more functions of course adds to the cost, a single box can still be more economical than separates because it eliminates several (perhaps pricey) cables and duplicate, expensive cases. A single box also tidies up the system, dramatically increasing its acceptability to the home's resident interior decorator.

There are disadvantages to the one-box approach: If one part of a system of separates fails, you don't have to bring the whole system to the repair shop; updates to separates are easier to make, though likely more expensive; and separate pre- and power amps offer flexibility in placement.

Some will argue that keeping the digital and analog circuits well apart offers audible benefits. I don't generally agree, particularly with well-designed productsand Classé's Sigma 2200i ($5500) is well designed and more: Inside its solid, spare, classic black case is every component and feature listed above.

Design
At a specified 200Wpc into 8 ohms (400Wpc into 4 ohms) and a net weight of 26.7 lbs, and with a lack of visible heatsinks, the Classé 2200i wouldn't be expected to include a conventional class-AB or class-A power amplifier, with the heavy transformers and thick, overbuilt chassis those technologies require. And it doesn't. The Sigma 2200i's amplifier is class-D, employing a switch-mode power supply and pulse-width modulation (PWM).

Nor is there an analog bypass: Incoming analog sources are immediately converted to a 24-bit/96kHz datastream. After passing through the digital preamp and signal-processing stages, the signal is converted to PWM at a high sampling rate of 384kHz, then fed in that form to the class-D amp. Finally, it's passed through a low-pass filter to eliminate the PWM signal's high-frequency carrier, and returned to an analog output to drive the speakers.

Regarding a class-D amp as "digital" is controversial, as many argue that PWM is not digital in the usual sense. PWM doesn't employ traditional D/A and A/D conversions. It does produce pulses at a high sampling rate, but these pulses represent the signal by varying in width. A traditional digital datastream comprises a string of identically sized bits grouped as "words." Each word is composed of ones and zeros and characterized by how many of each are included and how they're distributed.

While a short description of the 2200i won't distinguish it from most of the digital amplifiers now on the market, Classé maintains that they use proprietary digital technology that offers superior performance. The 2200i doesn't use the OEM class-D modules, typically from ICE or Hypex, on which most of today's digital amps are based. Instead, Classé uses a clean-sheet design that eliminates, they claim, the perceived sonic limitations of other class-D designs.

A more detailed discussion of PWM and of the Sigma 2200i's class-D operation would fill the rest of this review; those who want to dig deeper should check out Classé's white paper on the design of its CA-D200 power amplifier. Though not an integrated, the CA-D200 is the 2200i's technological father.

Do-All Classé
All of the Sigma 2200i's features can be controlled via its touchscreen and the Menu button to the left of the screen. (These are not directly duplicated on the remote, which offers limited setup control; see below.) To the right of the screen is a large, flush-mounted volume-control knob, which can also be used to adjust the balance, parametric EQ, tone controls, input offset, etc. The volume can be changed in increments of 0.5dB through the heart of the adjustment rangeI've seen other products, not all of them budget-priced, that offer steps of only 1dB, which in my opinion is too coarse. The volume setting is displayed on the screen when no other adjustments are being made, with numbers large enough to be easily read from across the room. The screen can be set to three levels of brightness, or to go dark after an adjustable timeout period.

To the left of the touchscreen are the Power/Standby button, headphone jack, and a USB host connector, for portable media devices and firmware updates, that supports inputs up to 24/192.

Around back are: high-quality, insulated, left and right speaker terminals; one balanced and two unbalanced analog inputs (one of the latter can be fitted with an optional phono stage for moving-magnet and moving-coil cartridges, not included in our review sample); four digital inputs (two TosLink optical for PCM up to 24/96, two coaxial for PCM up to 24/192); and two subwoofer outputs (one balanced, one unbalanced). An asynchronous USB port supports digital sources up to 24/192 and can mate with a USB host such as a PC or Mac computer. Also on the rear panel is a small, low-speed cooling fan. I never heard it operating.

Because of the pure-digital signal path from input to outputto just before the 2200i's final filter, which converts the PWM signal to analogpreamp out and power-amp in connections are not provided. And while, as noted above, the 2200i's digital inputs can accept source signals of up to 24/192 (it can't accept native DSD), these signals are immediately converted to 24/96, as all of the 2200i's digital processing is performed at that resolution.

Apart from its IR remote control, the 2200i offers no wireless connectivity. The rear panel's Ethernet connector can be used for Apple's AirPlay or DLNA, and can also support IP control of the 2200i via Classé's iOS or Android app (and/or home automation control) via a home network. There's also an IR input, for use with a repeater when the Classé is out of range of its IR wireless remote control, and an IR output to pass commands along to another Classé component.

Because the 2200i is a dedicated two-channel device, and not multichannel in any respect, its most unusual feature is the inclusion of four HDMI (v.2.0) inputs and one HDMI output, supporting up to 2160p (4K) video at up to 60Hz, plus audio (including Audio Return Channel, or ARC). HDCP 2.2 is included on HDMI input 4. The 2200i performs no video processing or scaling, and the audio carried by the HDMI cable must be two-channel PCM. The Classé will not decode bitstream Dolby Digital or DTS, so you must set your disc player to convert these formats to PCM. All Blu-ray and universal disc players I know of can do this.

If the above video technobabble makes little sense to you, all you really need to know is that the Classé will accept stereo audio or audio/video PCM sources via HDMI, process this stereo information as it does for other digital inputs, and, if needed, pass any compatible video along to a display from its HDMI output. Bottom line for those who may be interested in these HDMI capabilities: The Classé can serve as the heart of both a two-channel audio system and a 2.0-channel video setup.

The 2200i can also serve for 2.1-channelthat is, left and right speakers plus a mono-only subwoofer(s). It can be set up in one of three configurations: full-range main speakers with no sub; full-range mains plus sub with selectable low-pass filter frequencies and slopes of 6, 12, or 24dB/octave; and low-pass on the sub and high-pass on the mains with the same filter options. However, you must select the same rolloff rate and frequency for both the high- and low-pass filters: You can't mix and match. For example, you can't select 40Hz at 24dB/octave low-pass for the sub and 12dB/octave at 80Hz high-pass for the mains. (While such a split setup sounds odd, in some cases it can help to achieve a smoother response at the mains-to-subwoofer transition.) You can also leave the Classé's filters out entirely and rely on the sub's own filter(s) to keep it from singing along with the main channels. The 2200i offers no gain or phase controls for the subwoofer, so be sure that your sub does (most do).

The Classé offers some of the most extensive selections of tone-control and equalization options on the two-channel market. The tone controls can be used as either conventional bass and treble controls, or as a tilt control. While the defaults for the latter are 200 and 2000Hz (the ±3dB points), you can change these if desired. In tilt mode, the frequency balance is affected like a seesaw: the top end rises and the bottom end falls, or vice versa, as you tweak the control. In either case, the control limits are ±6dB.

There's more. Each channel of the 2200i offers six parametric-equalization (PEQ) filters with manually selectable center frequency, gain, and Q. (The Q is the width of the frequency band affected by the filter: the higher the number, the narrower the band.) Similar controls are offered for a connected subwoofer.

But while the tone and tilt features can be accessed and used intuitively by anyone, the PEQ filters should ideally be adjusted only with the help of in-room measurement equipment and the ability to use itand for most buyers, this will mean an experienced acoustical technician. The Classé's PEQs offer no automated setup, such as that provided by Anthem Room Correction (ARC) or Audyssey. At the September 2016 CEDIA Expo, Anthem introduced an ARC-equipped, two-channel integrated amp that could be a competitor for the Sigma 2200iwhile ARC offers the benefit of automation, Classé provides more flexible and personalized adjustments.

Many audiophiles blanch at the thought of using tone controls and/or EQ. With the Classé, you don't have to enable either, but they're provided for those who want them. All of the classic preamps referred to earlier offered tone controls. They weren't intended for room correction (in the Audio Paleolithic, no one thought about that), but rather as help for less-than-ideal recordings.

was this filter also used when measuring/presenting the (fig 9) 1kHz and (fig 10) 10kHz square wave screen shots?

No, the squarewave images were taken with just the external AP0025 filter as the AES17 brickwall filter would have affected the amplifier's reproduction of squarewaves. The AP0025's rolloff is sufficiently high in frequency not to have an effect other than eliminating RF noise.

Hello Thomas,
Thanks for the review of the Classe Sigma 2200i integrated. It was interesting to read your comments about the Classe Sigma 2200i being warm sounding tonally. I personally haven't heard the Sigma 2200i but have demoed the Sigma SSP + Sigma Amp5 combo paired with B&W speakers and Wilson Sabrina multiple times and they were very neutral tonally and very transparent imo. The Sigma combo were spectacular sonically. I demoed in both stereo for music in analog / digital bypass mode as well as for home theater (surrounds).

I would assume that the Sigma 2200i would perform very similar.
Did you get to listen to the Sigma separates by any chance?

I own the Sigma SSP and Sigma Amp 5. They sound spectacular for both home theater and two-channel audio. I have a Bluesound Vault2 connected to the Sigma SSP and high-resolution two-channel audio files sound terrific.

I also heard the Sigma 2200i demonstrated with Bowers & Wilkins 804 d3 speakers at a 2016 Music Matters event at my local dealer. Sounded fantastic. Heard four or five cuts (all Redbook format, interestingly, no high res) over the course of 40 minutes.